Airbase Damage Representation Improvements – Oct 2005


Introduction

The airbase damage model for conventional munitions has been updated and now uses the algorithm described in this document. This damage model is limited to determining the number of aircraft destroyed at the base and the time the airbase will return to an operational state. Special notes are:


The are two other airbase damage models based on the effects of biochem and nuclear attacks. These models have not been changed. For reference, the airbase degradation resulting from biological/chemical attack is still modeled as a reduction of sortie rates from the base that is cranked into the ATO module. And the nuclear damage model is still binary; that is the base is either killed or left intact.


Algorithm Overview

When an airbase is attacked with conventional munitions, the damage module can call a specific airbase damage model. Currently, the main controlling routine for conventional damage determination is bomb_em.F, found in the sim/environ directory. The pertinent changes to this algorithm are as follows:

  1. When the algorithm identifies targets in the detonation zone it identifies any airbases. The algorithm operates differently based upon the mission targeting inputs:

  2. If this mission was determined to focus exclusively on the airbase (either by mission specification or the Monte Carlo draw on unspecified missions), all further damage calculations are performed by the airbase_attrition_ algorithm, currently found in the sim/engment/survivability.c file (and described below). If the mission is not considered focused on the airbase (either by specific mission directives or according to the Monte Carlo draw), the standard approach of looping through all targets in the damage zone of the munitions drop(s) is performed to find all damaged assets. This calculation considers the spread of munitions based on targeting criteria, warhead guidance options, and CEP. The airbase is still considered as one of the candidate damage targets and could be damaged as a result of this calculation. Should one or more bombs be evaluated as attacking the base in this loop the airbase_attrition_ routine is again called. The change in this case is the airbase (and associated aircraft) damage estimate is based on the specific bomb(s) that are determined to hit the airbase, not the entire bombload delivered in this mission. The other bombs are mapped to damage against non-airbase targets.


As described above, the airbase_attrition_ routine is called only for damage calculations to airbases. The code is currently found in the sim/engment/survivability.c file. An overview of this algorithm is:

There are several simplifying step taken in this algorithm to streamline airbase specifications. First, the size of the aircraft doesn’t matter. Second, survivability does not consider aircraft dispersal at the base (generally the lowest cost passive survivability measure). Third, there’s no priority consideration for the type of aircraft to be protected. If studies require these considerations, please let us know and we’ll update the algorithm.


Using this survivability measure, the actual aircraft destroyed is evaluated against the munitions load as follows:

  1. The total number of targeted aircraft is estimated according to warhead guidance type. These estimates are as follows:

  1. When appropriate, the estimated total number of targeted aircraft is then adjusted according to submunitions as follows: The total number of bombs that fused is multiplied by (1-((submunitions*.2)*alog(urand_())). This adjustment is based upon the main unit targeting (hence the “1” factor) and a retargeting based upon a mean of one additional target per 5 submunitions taken from a negative exponential distribution.

  2. Based upon this targeting factor, the expectation of targeting any specific aircraft is (targeting factor)/(# aircraft at the base). Note that this is a expectation, not a probability, so values of more than 1 are legal and represent retargeting.

  3. Given these values, the algorithm loops through all aircraft at the base to determine their single strike probability of survivability as follows:

psone targeted bomb = ½ (/(kill radius/CEP)

where the kill radius is the specific munition kill radius (as defined in database prototyping) against the aircraft’s hardness (again, from database prototyping) times the survivability adjustment based on the likelihood the aircraft is in a hanger or revetment, as described above.


  1. Given this, the PK for each aircraft is:

PK = (1.- psone targeted bomb) (Expected Targeting)

Each aircraft’s survivability is Monte Carlo’ed versus this calculation and kills are recorded.

  1. Finally, the duration of airbase closure is computed as follows:

If more than two aircraft are killed:

Closure = (2*(# aircraft killed-2))*alog(urand_()) hours. This is a draw from a negative exponential distribution with a mean of two hours closure for each aircraft killed after the first one

Otherwise there’s no closure due to aircraft losses


In addition to this factor, an additional closure time is added it a munition designed for killing runways successfully hit the base. This closure is 12*(1+ alog(urand_()) hours This results in a closure of 12 hours plus an additional closure drawn from a negative exponential distribution with a mean of 12 hours. Thus the typical closure (I hesitate to say mean in a composite distribution) is 24 hours.


The computed airbase closure time is added to any preexisting closures to accommodate multiple strikes against the base.


Finally, it should be mentioned that the changeopstatus_ routine, in sim/objutil/asset_utilities.c, which is used to change asset operational status, has been changed to check that an event that re-opens an airbase does not attempt to re-open it before the damage has been cleaned up. This had to be done to recognize that an attack occurring while the airbase was being repaired would (usually) delay the reopening of the base and the original time to return operational would not be accurate.



New Database Prototyping Inputs

A new “Special Characteristics” attribute has been added to the warhead definition. The only operational item for this is “anti runway”


New Scenario Generation Inputs

The airbase specification GUI now incorporates information on the # of aircraft that can be parked in revetments and hangers at a base. To get to this interface edit the airbase in the Scenario Generation interface (shown on the left) and then select Special->Airbase Data”




Runtime Interface Changes

None


Data Analysis Changes

No changes. The information for killed aircraft is as before. No data is currently stored on airbase closures.